From whom do teeth and bones gain strength and firmness?

Nilgai belongs to the following family 

The best means of extinguishing petrol fires is-

An element that does not occur in nature but can be produced artificially is 

Which of the following is caused by the higher concentration of Nitrogen and Phosphorous? 

Is it a small quantity of additives to keep tomato chutney fresh for longer? 

Which proteins is main constituent of milk?

This organelle of the human body is known as the ‘powerhouse of the cell’. Name it from the given options.